In our production environment, we have been seeing Sidekiq processes
getting stuck randomly when a USR1 signal is sent to the Unicorn master
process. We have not been able to identify the root cause of why the
Sidekiq process gets stuck. We however noticed that when the Unicorn
master process receives a USR1 signal, it will reopen the logs for the
Unicorn master process first before sending a USR1 signal for the
Unicorn worker processes to reopen the logs. We figured that we should
do the same for the Sidekiq process as well when a USR1 signal.
In this commit, we introduce an arbitrary delay of 1 second before we
the Sidekiq process reopens its log files so as to allow enough time for the Unicorn
master to finish reopening it logs first.
We also do not send reopen logs for the Sidekiq process if the `DISCOURSE_LOG_SIDEKIQ`
env is not present because there is no need to reopen any logs.
We are seeing the following error in our logs when Sidekiq is sent a
`USR1` signal in production when logrotate happens:
```
log writing failed. stream closed in another thread
Error encountered while starting Sidekiq: can't be called from trap context\n/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/unicorn-6.1.0/lib/unicorn/util.rb:71:in `reopen'
```
I'm not quite sure where the error is triggered from so I'm improving
the way we log errors.
This commit introduces the following changes:
1. Introduce the `SignalTrapLogger` singleton which starts a single
thread that polls a queue to log messages with the specified logger.
This thread is necessary becasue most loggers cannot be used inside
the `Signal.trap` context as they rely on mutexes which are not
allowed within the context.
2. Moves the monkey patch in `freedom_patches/unicorn_http_server_patch.rb` to
`config/unicorn.config.rb` which is already monkey patching
`Unicorn::HttpServer`.
3. `Unicorn::HttpServer` will now automatically send a `USR2` signal to
a unicorn worker 2 seconds before the worker is timed out by the
Unicorn master.
4. When a Unicorn worker receives a `USR2` signal, it will now log only
the main thread's backtraces to `Rails.logger`. Previously, it was
`put`ing the backtraces to `STDOUT` which most people wouldn't read.
Logging it via `Rails.logger` will make the backtraces easily
accessible via `/logs`.
This commit updates all Sidekiq signal handling event logs to go through
Unicorn's logger instead of logging to STDOUT. Going through a proper logger
means the log messages are logged in the format which the logger has configured.
This means we get proper timestamp for the log messages.
Most of our logging goes through Rails.logger, and therefore appears in Logster at `/logs` on a site. The Sidekiq logger was bypassing this and writing directly to STDERR.
Unfortunately it's not possible to do `Sidekiq.logger = Rails.logger` because `Sidekiq#logger=` applies a number of patches to the logger instance, causing our whole logging system to break.
Instead, this commit adds a dedicated Logger instance with no output, which is then patched to forward all messages directly to `Rails.logger`
Unicorn uses the USR1 to indicate that log files should be reopened. This commit implements the same functionality for our forked sidekiq workers:
- USR1 is intercepted in the unicorn master, and re-issued to all child processes
- USR1 is trapped in the sidekiq processes, and `Unicorn::Util.reopen_logs` is used to re-open log files
Previously we had many places in the app that called `hostname` to get
hostname of a server. This commit replaces the pattern in 2 ways
1. We cache the result in `Discourse.os_hostname` so it is only ever called once
2. We prefer to use Socket.gethostname which avoids making a shell command
This improves performance as we are not spawning hostname processes throughout
the app lifetime
I introduced DemonBase because I had got some conflict between `demon/base.rb` and `jobs/base.rb`, however, to not rename base class, it is possible to use regex on absolute path in Zeitwerk custom inflector.
Zeitwerk simplifies working with dependencies in dev and makes it easier reloading class chains.
We no longer need to use Rails "require_dependency" anywhere and instead can just use standard
Ruby patterns to require files.
This is a far reaching change and we expect some followups here.
This reverts commit e805d44965.
We now have mechanisms in place to ensure heartbeat will always
be scheduled even if the scheduler is overloaded per: 098f938b
* FIX: Heartbeat check per sidekiq process
* Rename method
* Remove heartbeat queues of previous bootups
* Regis feedback
* Refactor before_start
* Update lib/demon/sidekiq.rb
Co-Authored-By: Régis Hanol <regis@hanol.fr>
* Update lib/demon/sidekiq.rb
Co-Authored-By: Régis Hanol <regis@hanol.fr>
* Expire redis keys after 3600 seconds
* Don't use redis to store the list of queues
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
This commit introduces an ultra low priority queue for post rebakes. This
way rebakes can never interfere with regular sidekiq processing for cases
where we perform a large scale rebake.
Additionally it allows Post.rebake_old to be run with rate_limiter: false
to avoid triggering the limiter when rebaking. This is handy for cases
where you want to just force the full rebake and not wait for it to trickle
This ensures that unicorn master forks of sidekiq run with a lower priority
than the webs. It means that a busy sidekiq is less likely to impact web
performance
This commit introduces 3 queues for sidekiq
"critical" for urgent jobs (weighted at 4x weight)
"default" for standard jobs(weighted at 2x weight)
"low" for less important jobs
"critical jobs"
Reset Password emails has been seperated to its own job
Heartbeat which is required to keep sidekiq running
Test email which needs to return real quick
"low priority jobs"
Notify mailing list
Pull hotlinked images
Update gravatar
"default"
All the rest
Note: for people running sidekiq from command line use
bin/sidekiq -q critical,4 -q default,2 -q low
